diff --git a/.travis.yml b/.travis.yml
index abb1cf2a..1c59030d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,7 +3,7 @@ language: php
 # lock distro so new future defaults will not break the build
 dist: trusty
 
-matrix:
+jobs:
   include:
     - php: 5.3
       dist: precise
@@ -16,12 +16,9 @@ matrix:
     - php: 7.3
     - php: 7.4
     - php: hhvm-3.18
-      install: composer require phpunit/phpunit:^5 --dev --no-interaction # requires legacy phpunit
   allow_failures:
     - php: hhvm-3.18
 
-sudo: false
-
 install:
   - composer install --no-interaction
 
diff --git a/tests/CallableStub.php b/tests/CallableStub.php
deleted file mode 100644
index a34a263a..00000000
--- a/tests/CallableStub.php
+++ /dev/null
@@ -1,10 +0,0 @@
-<?php
-
-namespace React\Tests\Dns;
-
-class CallableStub
-{
-    public function __invoke()
-    {
-    }
-}
diff --git a/tests/Query/TcpTransportExecutorTest.php b/tests/Query/TcpTransportExecutorTest.php
index ce9c845c..eae4d2c4 100644
--- a/tests/Query/TcpTransportExecutorTest.php
+++ b/tests/Query/TcpTransportExecutorTest.php
@@ -247,6 +247,10 @@ function ($e) use (&$wait) {
 
     public function testQueryStaysPendingWhenClientCanNotSendExcessiveMessageInOneChunkWhenServerClosesSocket()
     {
+        if (defined('HHVM_VERSION')) {
+            $this->markTestSkipped('Not supported on HHVM');
+        }
+
         $writableCallback = null;
         $loop = $this->getMockBuilder('React\EventLoop\LoopInterface')->getMock();
         $loop->expects($this->once())->method('addWriteStream')->with($this->anything(), $this->callback(function ($cb) use (&$writableCallback) {
diff --git a/tests/TestCase.php b/tests/TestCase.php
index 2c0c0cf1..6ea467e6 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -39,7 +39,13 @@ protected function expectCallableNever()
 
     protected function createCallableMock()
     {
-        return $this->getMockBuilder('stdClass')->setMethods(array('__invoke'))->getMock();
+        if (method_exists('PHPUnit\Framework\MockObject\MockBuilder', 'addMethods')) {
+            // PHPUnit 9+
+            return $this->getMockBuilder('stdClass')->addMethods(array('__invoke'))->getMock();
+        } else {
+            // legacy PHPUnit 4 - PHPUnit 9
+            return $this->getMockBuilder('stdClass')->setMethods(array('__invoke'))->getMock();
+        }
     }
 
     public function setExpectedException($exception, $exceptionMessage = '', $exceptionCode = null)